Fig. 3.

HRF field curvature and distortion. Theoretical (a) field curvature and (b) distortion plotted as a function of distance from the center of the image. Field curvature does not exceed 1.1 mm and the maximum distortion is 0.20%. (c) Experimental distortion was measured by imaging a $100\text{-}\mu \mathrm{m}\text{-square}$ grid target, yielding a maximum measured distortion of 0.29% at the edge of the image.